The ability of users to access programs and share data over local area networks (referred to as “LANs”) has become a necessity for most working environments. To improve efficiency and ease of use, certain enhancements may be added to a LAN such as remote wireless access. By providing remote wireless access, a wireless LAN (WLAN) is formed.
As described in U.S. Pat. No. 5,987,062 issued to Netwave Technologies, Inc., now owned by Nortel Networks Limited, one type of WLAN employs dedicated stations, which are referred to as access points (APs). Therein, each AP is a relay station that receives frames from a mobile unit such as a notebook-type computer with a suitable adapter card as described in U.S. Pat. No. 5,987,062. Thereafter, the AP transmits contents of these frames, namely one or more data packets, to the fixed backbone network.
Of course, the AP also receives data packets of data from the fixed backbone network for transmission to one or more mobile units. In accordance with Institute of Electrical and Electronics Engineers (IEEE) 802.11 published Nov. 16, 1998 and entitled “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications,” the AP is capable of detecting whether a data packet is directed toward a specific mobile unit (referred to as “unicast frame”). Such detection is accomplished by examining a destination address from the incoming data packet and comparing this address to Media Access Control (MAC) addresses for each of its authenticated mobile units. The MAC addresses are stored in an address table maintained within the AP. If a match is detected, the data packet is sent to a wireless transceiver interface 210 to produce a unicast frame having the MAC address as its destination address. Upon receiving the contents of the unicast frame, the mobile unit transfers an acknowledgement (ACK) frame to the AP in accordance with IEEE 802.11.
Besides unicast transfers, the AP also supports the transmission of data frames to a group of mobile units (referred to as “multicast frames”) or to all of the mobile units (referred to as a “broadcast frames”). In accordance with IEEE 802.11, the delivery of multicast and broadcast frames is not reliable because ACK frames are not required from the mobile units. Currently, there is no protocol for the AP to confirm whether any of its multicast or broadcast frames have been successfully received by the MUs. Since information within the multicast or broadcast frames may be vital to the operations of the WLAN, insuring their receipt would enhance the capability of the APs.